1. Characterization of semi-quadrics. A survey;Buekenhout;Coll. Int. Theorie Comb. Roma 1973. Atti Conv. Lincei,1976
2. Generalized quadrangles in projective spaces;Buekenhout;Arch. Math.,1974
3. Partial geometries, generalized quadrangles and strongly regular graphs;Higman,1971
4. C. Lefèvre-Percsy, Espaces polaires dégénérés des espaces projectifs, Simon Stevin (to appear).
5. C. Lefèvre-Percsy, Espaces polaires faiblement plongé dans un espace projectif, J. Geometry (to appear).